1. Field of the Invention
The present invention relates to a printed circuit board mounting assembly and, more particularly, to a printed circuit board mounting assembly installed in a housing of a thin electrical system such as a portable computer.
2. Discussion of Related Art
The development of computer technology induced various models of a computer such as a notebook computer, wallet personal computer (PC), personal digital assistant (PDA), and a hand-held personal computer (HPC). Therefore, the scope of usage has rapidly expanded. The computer trend is towards miniaturization and a slim design to allow for portability.
In the course of trying to make smaller and thinner portable computers, the space taken to mount a printed circuit board has become a design limitation. The circuit boards such as the main board, also called the motherboard, has key electronics for the function of the portable computer such as a microprocessor or a central processing unit (CPU) that controls the function of the portable computer, disk controllers that control permanent storage, and the random access memory for temporary data storage. A certain amount of space is needed in the housing of the portable computer to mount such a circuit board. As the portable computer becomes thinner, the mounting structures are reduced also and thereby losing some stability in the process. A stable circuit board is very important because if it is not stable then key components of the portable computer may be damaged.
Another problem in portable computers has been reducing the noise caused by electromagnetic interference (herein after referred to as "EMI"). Excessive amounts of EMI can affect the electrical functioning of the portable computer and outside electrical devices. Because of the size limitations, special structures that may take up space for reducing the EMI are discouraged.
An exemplar of the prior art Ohgami et al. (U.S. Pat. No. 5,689,400, Portable Electronic Apparatus Including Space-saving Component Mounting Features, Nov. 18, 1997) discloses a fairly large bracket that is used to mount the printed circuit board in a portable computer. Annis et al. (U.S. Pat. No. 5,436,803, EMI Shielding having Flexible Conductive Envelope, Jul. 25, 1995) discloses an electrically insulating flexible sheet such as polyethylene with embedded conductive fibers that forms an electromagnetic interference shielding enclosure for a circuit card within a portable computer. Such a structure takes up valuable space. Nakamura et al. (U.S. Pat. No. 5,784,256, Portable Computer having a Circuit Board Including a Heat-Generating IC Chip and a Metal Frame Supporting the Circuit Board, Jul. 21, 1998) discloses raised bosses supported by relatively large supporting walls around part of the bosses. The supporting walls subdivides the portable computer into smaller sections thereby limiting the available surface area needed to include other electrical structures. Nigro, Jr. et al. (U.S. Pat. No. 4,742,478, Housing for a Portable Computer, May 3, 1988) discloses fairly long bosses for mounting printed circuit boards. Lin et al (U.S. Pat. No. 5,036,313, Portable Computer with Improved Assembly Design, July 1991) discusses a portable computer housing assembly. The upper housing is connected to the lower housing using fasteners inserted though a bosses molded on the lower housing. A separate rail molding allowing for the printed circuit board to slide in is used. The rails take up more space needed for electronic parts.